Methods for depositing metal films onto diffusion barrier layers by CVD or ALD processes

ABSTRACT

A process is described for depositing a metal film on a substrate surface having a diffusion barrier layer deposited thereupon. In one embodiment of the present invention, the process includes: providing a surface of the diffusion barrier layer that is substantially free of an elemental metal and forming the metal film on at least a portion of the surface via deposition by using a organometallic precursor. In certain embodiments, the diffusion barrier layer may be exposed to an adhesion promoting agent prior to or during at least a portion of the forming step. Suitable adhesion promoting agents include nitrogen, nitrogen-containing compounds, carbon-containing compounds, carbon and nitrogen containing compounds, silicon-containing compounds, silicon and carbon containing compounds, silicon, carbon, and nitrogen containing compounds, or mixtures thereof. The process of the present invention provides substrates having enhanced adhesion between the diffusion barrier layer and the metal film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/428,447, filed May 2, 2003, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates to a diffusion barrier layer and methodcomprising same upon which a metal film, preferably a copper film, isdeposited thereupon. More specifically, the present invention relates toa diffusion barrier layer and method comprising same that improves theadhesion between the diffusion barrier layer and the metal layer.

As the microelectronics industry evolves into ultra-large-scaleintegration (ULSI), the intrinsic properties of typical metallizationmaterials become the limiting factor in advanced circuit design andmanufacture. Aluminum, which has been widely used as the interconnectmetal, suffers from several drawbacks such as relatively high electricalresistivity and susceptibility to electromigration which may curtail itsusefulness. Other metallization materials, such as tungsten andmolybdenum, provide a high migration resistance but also have a highelectrical resistance that prevents an integrated circuit incorporatingthese materials from being operated at high speed. Because of its lowresistivity and enhanced resistance to electromigration, copper is anattractive material for high-speed integrated circuits. Still othercandidates being considered for use as a metallization material includeplatinum, cobalt, nickel, palladium, ruthenium, rhodium, iridium, gold,silver and alloys comprising same.

Numerous methods such as ionized metal plasma (IMP), physical vapordeposition (PVD), chemical vapor deposition (CVD), atomic layerdeposition (ALD), plasma-assisted chemical vapor deposition (PACVD),plasma-enhanced chemical vapor deposition (PECVD), electroplating, andelectroless plating have been used to deposit a metal film such ascopper upon a barrier layer. Among them, CVD and ALD methods using oneor more organometallic precursors may be the most promising methodsbecause these methods provide excellent step coverage for high aspectratio structures and good via filling characteristics.

Several organometallic precursors have been developed to deposit lowelectrical resistivity copper films by the aforementioned processes,particularly CVD or ALD processes. Two of the most useful families ofcopper CVD precursors that have been studied extensively are the Cu (I)and Cu (II) β-diketonates. The Cu (II) precursors require use of anexternal reducing agent such as hydrogen or alcohol to deposit copperfilms that are largely free of impurities, while Cu (I) precursors candeposit pure copper films without using an external reducing agent via abimolecular disproportionation reaction that produces a Cu (II)β-diketonate as a volatile byproduct. The β-diketonate ligand most oftenpresent in these precursors is hexafluoroacetylacetonate or the hfacanion [OC(CF₃)CHC(CF₃)O]⁻. A particularly effective CVD copper precursoris 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato-copper (I)trimethylvinylsilane (hereinafter Cu(hfac)(tmvs)), which is sold underthe trademark CUPRASELECT™ by the Schumacher unit of Air Products andChemicals, Inc., Carlsbad, Calif., the assignee of the presentinvention.

A barrier layer is typically utilized in conjunction with a metal orcopper layer to prevent detrimental effects caused by the interaction ordiffusion of the metal or copper layer with other portions of theintegrated circuit. Exemplary barrier materials include metals, such astitanium, tantalum, tungsten, chromium, molybdenum, zirconium, vanadium,and carbides, nitrides, carbonitrides, silicon carbides, siliconnitrides, and silicon carbonitrides of these metals where theyconstitute a stable composition. In some instances, the initialdeposition of CVD or ALD metal or copper film on the barrier layer mayfunction as a seed layer, e.g., an adhesive, conducting seed layer tofacilitate further deposition of a subsequent metal layer such as copperby electrochemical plating, electroless plating, or by PVD, CVD, or ALDmethods to complete the thin-film interconnect.

Despite the foregoing developments, the integrated circuit (IC) industryis presently experiencing difficulty forming adherent metal or copperfilms on diffusion barrier layer materials. A variety of solutions tothis problem have been proposed. For example, Gandikota et al.,Microelectronic Engineering 50, 547-53 (2000), purports to improveadhesion between a CVD copper thin film and barrier layers by: (a)depositing a copper flash layer on the barrier layer by physical vapordeposition (PVD) prior to chemical vapor deposition, or (b) annealingthe CVD copper layer after deposition. See also Voss et al.,Microelectronics Engineering 50, 501-08 (2000). Unfortunately, thesemethods are not acceptable to the IC industry because they add to theequipment requirements for the copper deposition step. In addition,annealing, particularly at elevated temperatures, can have deleteriouseffects on the overall product.

U.S. Pat. No. 5,019,531 discloses a CVD process for depositing copper ona substrate selected from the group consisting of aluminum, silicon,titanium, tungsten, chromium, molybdenum, zirconium, tantalum, vanadiumand silicides thereof using an organic complex or organometalliccompound of copper. The organic complex or organometallic compound isselected from β-diketonate and cyclopentadienyl compounds of copper suchas bis-acetylacetonato-copper, bis-hexafluoroacetylacetonato-copper,bis-dipivaloylmethanato-cooper, dimethyl-gold-hexafluoroacetylacetonato,cyclopentadienyl-triethylphosphine-copper, anddimethyl-gold-acetylacetonato. The adhesion of the copper on thesubstrate, however, was poor.

As mentioned previously, one method to form a copper film unto asubstrate having a barrier layer deposited thereupon is through plasmaenhanced or plasma assisted chemical vapor deposition. The reference,Eisenbraun et al., “Enhanced Growth of Device-Quality Copper by HydrogenPlasma-Assisted Chemical Vapor Deposition” published in Appl. Phys.Letter, 1992), describes a PACVD process for depositing copper usingβ-diketonate precursors. According to Eisenbraun, the copper precursoris reduced by atomic and ionic hydrogen species to deposit copper on thesubstrate. The reference, Jin et al., Plasma-Enhanced Metal OrganicChemical Vapor Deposition of High Purity Copper Thin Films Using PlasmaReactor with the H Atom Source” published in J. Vac. Sci. Technology A,1999, also discloses a plasma-enhanced technique to deposit pure copperusing Cu(II) bis(hexafluoroacetylacetonato), Cu(II)(hfac), as anorganometallic precursor. Likewise, the reference, Laksmanan et al., “ANovel Model of Hydrogen Plasma Assisted Chemical Vapor Deposition ofCopper” and published in Thin Solid Films, 1999, describes ahydrogen-plasma assisted process for depositing copper on a barrierlayer. Although, the aforementioned references were successful indepositing a metallic, continuous, dense device-quality copper film withconformal step coverage that was virtually free from heavy elementcontaminants, the adhesion of copper on the substrate was unacceptable.

U.S. Pat. Nos. 5,085,731, 5,094,701 and 5,098,516 (referred tocollectively as Norman) describe a thermal CVD process for depositing acopper film with low electrical resistivity by using a volatile liquidorganometallic copper precursor such as Cu(hfac)(tmvs) at relatively lowtemperatures onto metallic substrates. Further, the reference, Norman etal. “Chemical Additives for Improved Copper Chemical Vapor DepositionProcessing”, Thin Solid Films, 1995, describes the use of tmvs and hfacligands alone or in combination with water to improve deposition ofcopper. This deposition was achieved, however, with limited success.Numerous other researchers investigated the use of tmvs and hfac ligandsalone or in combination with water to improve deposition of copper withlimited or no success (e.g., Petersen et al. “Enhanced Chemical vaporDeposition of Copper from (hfac)Cu(TMVS) Using Liquid Coinjection ofTMVS”, J. Electrochem. Soc., 1995; Gelatos et al. “Chemical VaporDeposition of Copper from Cu⁺¹ Precursors in the Presence of WaterVapor” Appl. Phys. Letter, 1993; Japanese Unexamined Patent PublicationJP 2000-219968A; and U.S. Pat. No. 6,165,555).

Other organometallic copper precursors, such as (hfac)Cu(I)(MP) where MPis 4-methyl-1-pentene and (hfac)Cu(I)(DMB) where DMB is3,3-dimethyl-1-butene, have been used to deposit low resistivity copperfilms on silicon wafers coated with titanium nitride (Kang et al.,“Chemical Vapor Deposition of Copper Film”, Thin Solid Films, 1999). Inthe reference, Hwang et al., “Surfactant-Catalyzed Chemical VaporDeposition of Copper Thin Films”, Chem. Mater., 2000, a submonolayer ofiodine has been used to facilitate deposition of copper films fromCu(hfac)(tmvs) with a smooth surface and at a greatly enhanced rate.None of these techniques, however, discusses the quality of the CVDdeposited copper film on the barrier layer.

U.S. Pat. No. 6,423,201 B1 describes the use of a thin silicon layer atthe top of a TiN barrier layer to improve adhesion. It is, however, notdesirable to deposit copper directly on silicon due to the formation ofcopper silicon alloys which exhibit high resistivity.

The adhesion of copper to the underlying barrier materials has also beenreported to be problematic by several researchers. For example, thedeposition of copper on titanium nitride substrate usingCu(I)(hfac)(tmvs) precursor (or CUPRASELECT™) has been reported to bepoor (Nguyen, T. and Evans, D. R., “Stress and Adhesion of CVD Copperand TiN”, Mat. Res. Soc. Symp. Proc., 1995 and Nguyen, T. and Evans, D.R., “Stress and Adhesion of CVD Copper and TiN”, Mat. Res. Soc. Symp.Proceeding, 1995). It has been reported that the direct deposition ofCVD copper on a diffusion barrier leads to the formation of a fluorine,carbon and oxygen containing amorphous layer between the copper film andbarrier layer that is responsible for poor adhesion, as discussed byKroger, R. et al. in papers “Nucleation and Growth of CVD Copper Films”published in Mat. Res. Soc. Symp. Proceeding, 1999 and “Properties ofCopper Films Prepared by Chemical Vapor Deposition for AdvancedMetallization of Microelectronic Devices” published in J.Electrochemical Society, 1999. The amorphous layer is believed to beformed during very early stages of CVD copper deposition from theby-products of the Cu (I) precursor. Similar adhesion problems onbarrier layer have been reported with Cu (II) precursors.

The reference WO 00/71550 discusses limiting the formation of afluorine, carbon and oxygen containing amorphous layer on the barrierlayer by reducing and/or eliminating the amount of fluorine present inthe copper precursors. However, these attempts have not yet resulted inthe desired results.

Reduction of copper precursors like Cu (II)bis-(2,2,6,6-tetramethyl-3,5-heptanedionate) with hydrogen and Cu (II)bis-(1,1,1,5,5,5-hexafluoroacetylactonate) hydrate with methanol,ethanol, and formalin have been tried to deposit copper by atomic layerepitaxy on a variety of barrier layers with limited success, asdescribed by Martensson and Carlsson in “Atomic Layer Epitaxy ofCopper”, J. Electrochem. Soc., 2000 and Solanki and Pathangey in “AtomicLayer Deposition of Copper Seed Layers”, Electrochemical and Solid-StateLetters, 2000.

The reference, Holloway et al. in a paper “Tantalum as a DiffusionBarrier Between Copper and Silicon: Failure Mechanism and Effect ofNitrogen Additions” published in J. Appl. Physics, 1992, relates thattantalum nitride (Ta₂N) is an excellent barrier to copper penetration.However, the reference fails to discuss the deposition of copper by CVDon tantalum nitride nor the quality of CVD copper adhesion onto thetantalum nitride.

The barrier properties of CVD and sputtered tantalum nitride have beenstudied and compared by Tsai et al. in a paper “Comparison of theDiffusion Barrier Properties of Chemical-Vapor Deposited and SputteredTaN between Cu and Si” published in J. Appl. Physics, 1996. However, thereference fails to discuss the deposition of copper by CVD on tantalumnitride nor the quality of CVD copper adhesion onto the tantalumnitride.

Despite the foregoing developments, there remains a need to develop aprocess to improve the adhesion of a metal, particularly a copper, filmdeposited on a diffusion barrier layer by CVD or ALD. Further, there isa need for a process to improve the adhesion of the metal film onto thebarrier layer without incurring additional equipment requirements or anannealing step.

All references cited herein are incorporated herein by reference intheir entireties.

BRIEF SUMMARY OF THE INVENTION

The present invention satisfies one, if not all, of the needs in the artby providing a method for forming a metal layer, preferably a copperfilm, onto at least a portion of the surface of a substrate having adiffusion barrier layer deposited thereupon. Specifically, in one aspectof the present invention, there is provided a process for forming ametal film on a surface of a diffusion barrier layer comprising:providing at least one surface of the diffusion barrier layer whereinthe diffusion barrier layer is comprised of at least one materialselected from the group consisting of a metal, a metal carbide, a metalnitride, a metal carbonitride, a metal silicon carbide, a metal siliconnitride, a metal silicon carbonitride, or a mixture thereof and whereinthe at least one surface is substantially free of an elemental metal;and forming the metal film on at least one surface using at least oneorganometallic precursor provided that when the diffusion barrier layer(i) has a material that is the metal, (ii) has an orientation other thana preferred (111) orientation, and/or (iii) has less than 95% preferred(111) orientation; then the step of exposing at least one surface of thediffusion barrier layer to at least one adhesion promoting agentselected from the group consisting of a nitrogen, a nitrogen-containingcompound, a carbon-containing compound, a carbon and nitrogen containingcompound, a silicon-containing compound, a silicon and carbon containingcompound, a silicon, carbon, and nitrogen containing compound or amixture thereof is conducted.

In another aspect of the present invention, there is provided a processfor forming a substantially continuous copper film on a surface of adiffusion barrier layer comprising: providing a substrate comprising adiffusion barrier layer wherein the diffusion barrier layer is comprisedof at least one material selected from the group consisting of a metal,a metal carbide, a metal nitride, a metal carbonitride, a metal siliconcarbide, a metal silicon nitride, a metal silicon carbonitride, or amixture thereof; exposing the surface of the diffusion barrier layer toan adhesion promoting agent selected from the group consisting ofnitrogen, a nitrogen-containing compound, a carbon-containing compound,a carbon and nitrogen containing compound, a silicon-containingcompound, a silicon and carbon containing compound, a silicon, carbon,and nitrogen containing compound, or mixtures thereof; and forming thecopper film on the at least a portion of the surface via the depositionwith an organometallic copper precursor.

In another aspect of the present invention, there is provided a processfor forming a substantially continuous metal film on a surface of adiffusion barrier layer comprising: providing a substrate comprising adiffusion barrier layer wherein the diffusion barrier layer is comprisedof at least one material selected from the group consisting of a metalcarbide, a metal nitride, a metal carbonitride, a metal silicon carbide,a metal silicon nitride, a metal silicon carbonitride, or a mixturethereof and wherein the diffusion barrier layer comprises asubstantially (111) preferred orientation and forming the metal film onthe surface of the diffusion barrier layer via the deposition with anorganometallic precursor.

In yet another aspect of the present invention, there is provided aprocess for forming a substantially continuous metal film on a surfaceof a diffusion barrier layer comprising: providing a substratecomprising a diffusion barrier layer wherein the diffusion barrier layeris comprised of at least one material selected from the group consistingof a metal, a metal carbide, a metal nitride, a metal carbonitride, ametal silicon carbide, a metal silicon nitride, a metal siliconcarbonitride, or a mixture thereof; exposing the surface of thediffusion barrier layer to an adhesion promoting agent selected from thegroup consisting of nitrogen, a nitrogen-containing compound, acarbon-containing compound, a carbon and nitrogen containing compound, asilicon-containing compound, a silicon and carbon containing compound, asilicon, carbon, and nitrogen containing compound, or mixtures thereof;and growing a metal film on the surface of a the diffusion barrier layerby contacting the surface with a halogen-containing precursor and anorganometallic precursor wherein the halogen and the metal within theprecursors react to form a metal halide layer; and exposing the metalhalide layer to a reducing agent to provide the metal film.

In another aspect of the present invention, there is provided a processfor forming a substantially continuous metal layer on an at least onesurface of a diffusion barrier layer, the process comprising: providinga substrate comprising the diffusion barrier layer within a vacuumchamber wherein at least one exposed surface of the diffusion barrierlayer is substantially free of an elemental metal; introducing an atleast one organometallic precursor into the vacuum chamber; and applyingenergy to the at least one organometallic precursor to induce reactionof the organometallic precursor to deposit the substantially continuousmetal layer on the at least one surface of the diffusion barrier layer.

These and other aspects of the present invention will be more apparentfrom the following description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for depositing a metal film on asubstrate surface having a diffusion barrier layer wherein the metalfilm is deposited on the barrier layer by the chemical vapor depositionor atomic layer deposition with an organometallic precursor. Theresultant metal film may have an increased adherence to the underlyingbarrier layer. The prior art has disclosed a variety of methods fordepositing metal films, such as copper films, onto surfaces of asubstrates and/or barrier layers using an organometallic precursors,particularly fluorinated precursors. The resultant films of the priorart, unfortunately, have relatively poor adherence to the underlyingdiffusion barrier layer.

The problem of poor adherence of the metal film onto the diffusionbarrier layer may be attributable to the presence of CF₃ radicals on thebarrier layer when a fluorinated organometallic precursor is used todeposit the metal layer. In embodiments wherein a copper film isdeposited, the deposition of the diffusion barrier layer and the copperlayer is generally conducted in a cluster tool equipped with a number ofchambers operated under vacuum. The barrier layer can be deposited ontoa substrate such as a silicon wafer either by CVD, ALD, or PVD in onechamber and then transferred to another chamber for the deposition ofthe copper film. Because of the use of the organometallic copperprecursor in the chamber for prior depositions of copper, the chambermay be contaminated with fragments or dissociated species of theorganometallic copper precursor such as CF₃ radicals. The CF₃ radicalsmay react with the exposed metal in the barrier layer, leading to theformation of a fluorine, carbon and oxygen containing amorphous layerbetween the copper film and the barrier layer. The formation of thisamorphous layer may thereby compromise the adhesion between these twolayers.

As mentioned previously, one particularly preferred fluorinatedorganometallic copper precursor is Cu(I)(hfac)(tmvs). While notintending to be bound by theory, there are believed to be two mechanismsinvolved when depositing copper using Cu(I)(hfac)(tmvs). The firstmechanism may be a simple disproportianation reaction wherein copper isdeposited on a substrate that is not chemically active towards degradingthe precursor without breaking the C—CF₃ bonds contained in the ‘hfac’ligand. The product from the disproportionation reaction such asCu(II)(hfac)₂ may be volatile in nature and can be removed from thechamber without further disintegration leaving elemental Cu to bedeposited onto the substrate surface. The second mechanism, however,which is encountered when the precursor is introduced to a barriermaterial such as tantalum which is chemically reactive, involves thebreakdown of the C—CF₃ bonds in the Cu(I)(hfac)(tmvs) molecule. Thisprocess may produce fragments such as CF₃ radicals that are extremelyreactive thereby causing the formation of an undesirable amorphous layerof chemical debris on the barrier layer. Consequently, it may bedesirable to avoid the breakdown of Cu(I)(hfac)(tmvs) molecule duringthe deposition process. Alternatively, it may be desirable to make thebarrier layer non-reactive to the fragments or dissociated species ofthe Cu(I)(hfac)(tmvs) molecule to deposit the copper film on at least aportion of the barrier layer with improved adhesion. While the previousexample discusses depositing copper films with a organometallic copperprecursor, it is believed that the method of the present invention isapplicable to the deposition of other metal films besides copper such asplatinum, nickel, cobalt, palladium, ruthenium, rhodium, irridium, goldand silver, etc. with organometallic precursors such as organometallicplatinum precursors, organometallic nickel precursors, organometalliccobalt precursors, organometallic palladium precursors, organometallicruthernium precursors, organometallic iridium precursors, organometallicgold precursors, organometallic silver, etc.

One attempt to render the surface of the barrier layer non-reactive tothe dissociated species of the organometallic precursor is by thedeposition of a thin, flash layer of metal onto the barrier layer usinga physical vapor deposition technique such as sputtering. The thin layerof metal may be chemically inert towards the dissociated species of theorganometallic precursor thereby preventing the formation of a fluorine,carbon and oxygen containing amorphous layer on the metal film.Unfortunately, the addition of an additional chamber to a productionline to deposit a flash layer of metal may be prohibitively expensive.Further, the flash layer of metal is an incomplete solution to theadherence problem because the flash layer resides primarily at the baseof deeply etched features such as vias or lines. The sidewalls of thesefeatures are still exposed to the organometallic precursor in subsequentprocessing steps. Therefore, the key to achieving adhesion between themetal and barrier layer is to render the barrier layer substantiallyunreactive towards the dissociated species of the organometallicprecursor.

The present invention provides a method to improve the adhesion of ametal film, preferably a copper film, upon at least a portion of thebarrier layer by providing at least a portion of the barrier layer thatmay be substantially non-reactive to the fragments of the dissociatedorganometallic precursor molecule. Further, in some embodiments, thebreakdown of the organometallic precursor into dissociated species maybe avoided. It is thus surprising and unexpected that the deposition ofa substantially continuous metal film onto at least a portion of thebarrier layer having relatively good adhesion may be achieved byavoiding exposure of an elemental metal present on the surface of thebarrier layer to the organometallic precursor and/or any dissociatedfragments of the organometallic precursor. In this connection, at leasta portion of the barrier layer surface may be substantially free of anelemental metal. A substantially metal-free barrier layer surface may beachieved through: (a) providing a metal nitride, metal carbide, metalcarbonitride, metal silicon carbide, metal silicon nitride, metalsilicon carbonitride barrier layer with a substantially (111) preferredorientation (i.e., at least 95% or greater (111) preferred orientation);(b) exposing a metal nitride, metal carbide, metal carbonitride, metalsilicon carbide, a metal silicon nitride, or a metal siliconcarbonitride barrier layer with a (111) preferred orientation below 95%to an adhesion promoting agent prior to the formation of the metallayer; (c) exposing a surface of the metal nitride, metal carbide, metalcarbonitride, a metal silicon carbide, a metal silicon nitride, or ametal silicon carbonitride barrier layer with an orientation other thana (111) preferred orientation with an adhesion promoting agent prior tothe formation of the metal layer; and (d) exposing the surface of ametal barrier layer to an adhesion promoting agent prior to theformation of the metal layer. Examples of orientations other than a(111) preferred orientation include, but are not limited to, a (100)preferred orientation, a (200) preferred orientation, or an amorphouslayer. The adhesion promoting agent may be at least one agent selectedfrom the group consisting of nitrogen, nitrogen-containing compoundssuch as ammonia, carbon-containing compounds such as methane, ethane,propane, ethylene, acetylene, propylene, etc., carbon and nitrogencontaining compounds such as amines, silicon-containing compounds suchas silane and disilane, silicon and carbon containing compounds such asmethyl silane, dimethyl silane, trimethyl silane, etc., and silicon,carbon, and nitrogen containing compounds such as trimethylsilylcyanide,1-trimethylsilylimidazole, etc., or mixtures thereof. Avoiding thepresentation on the exposed metal in the surface of the barrier layer tothe organometallic precursor, particularly dissociated species of anorganometallic precursor, can minimize or eliminate the formation of theundesirable amorphous layer thereby resolving the adhesion problem.

The diffusion barrier layer of the present invention may be comprised ofa material such as a metal, a metal carbide, a metal nitride, a metalcarbonitride, a metal silicon nitride, a metal silicon carbide, a metalsilicon carbonitride, or a mixture thereof. Exemplary metals suitablefor use in the present invention include titanium, tungsten, chromium,tantalum, molybdenum, zirconium, vanadium, or mixtures thereof. Someexemplary metal carbides include titanium carbide, tungsten carbide,tantalum carbide, chromium carbide, molybdenum carbide, vanadiumcarbide, zirconium carbide, or mixtures thereof. Exemplary metalnitrides include, but are not limited to, titanium nitride, tungstennitride, tantalum nitride, chromium nitride, molybdenum nitride,zirconium nitride, vanadium nitride, or mixtures thereof. Exemplarymetal carbonitrides include titanium carbonitride (TiCN), tantalumcarbonitride (TaCN), chromium carbonitride, tungsten carbonitride,molybdenum carbonitride, zirconium carbonitrides, or mixtures thereof.Exemplary metal silicon nitrides include titanium silicon nitride(TiSiN), molybdenum silicon nitride (MoSiN), etc. Exemplary metalsilicon carbides include titanium silicon carbide (TiSiC), tungstensilicon carbide (WSiC), etc. Exemplary metal silicon carbonitridesinclude silicon carbonitride, titanium silicon carbonitride, andtantalum silicon carbonitride, etc. In certain embodiments of thepresent invention wherein the diffusion barrier layer is comprised of amaterial other than a pure metal (i.e., metal carbide, metal nitride,metal carbonitride, metal silicon carbide, metal silicon nitride, ormetal silicon carbonitride), the surface of the barrier layer may have asubstantially (111) preferred orientation, i.e., has 95% or greater(111) preferred orientation, to avoid the need for the additional stepof exposing the surface to an adhesion promoting agent. In theseembodiments, at least a portion of the diffusion barrier surface mayalso be substantially pure, i.e., have a material purity of 95% orgreater.

The diffusion barrier layer can be deposited by a variety of processessuch as, but not limited to, chemical vapor deposition (CVD), atomiclayer deposition (ALD), or physical vapor deposition (PVD) processes.Some examples of CVD processes that may be used to form the barrierlayer include the following: thermal chemical vapor deposition, plasmaenhanced chemical vapor deposition (“PECVD”), high density PECVD, photonassisted CVD, plasma-photon assisted (“PPACVD”), cryogenic chemicalvapor deposition, chemical assisted vapor deposition, hot-filamentchemical vapor deposition, photo initiated chemical vapor deposition,CVD of a liquid polymer precursor, deposition using supercriticalfluids, or transport polymerization (“TP”). These processes may be usedalone or in combination. In certain preferred embodiments, thedeposition of the barrier layer is conducted at a temperature rangingfrom 100 to 425° C., preferably from 150 to 400° C. In certain otherpreferred embodiments, the deposition is conducted under vacuum at apressure ranging from 10⁻⁹ torr to 400 torr, preferably from 1 millitorrto 100 torr. Although the chemical reagents used herein may be sometimesdescribed as “gaseous”, it is understood that the chemical reagents maybe delivered directly as a gas to the reactor, delivered as a vaporizedliquid, a sublimed solid and/or transported by an inert carrier gas intothe reactor. A reducing gas such as hydrogen can optionally be usedduring the deposition of the barrier layer.

In certain embodiments, PVD processes, such as sputtering, reactivesputtering, etc. may be used to deposit metal nitride, metal carbide,metal carbonitride, metal silicon nitride, metal silicon carbide, ormetal silicon carbonitride barrier layers with and without a (111)preferred orientation. The extent of metal nitride, metal carbide, ormetal carbonitride material with (111) preferred orientation present inthe film can be adjusted by manipulating deposition parameters includingthe sputtering rate, the applied power and bias, the partial pressure ofreactive gas such as nitrogen, ammonia or a hydrocarbon gas, thedeposition temperature and pressure, etc. If the barrier layer does nothave a substantially (111) preferred orientation, the barrier layer canbe exposed to an adhesion promoting agent such as any of the agentsdisclosed herein prior to depositing the metal by CVD or ALD processes.The exposure to an adhesion promoting agent is preferably conducted at atemperature and pressure similar to that used to deposit the metalnitride, metal carbide, metal carbonitride, metal silicon nitride, metalsilicon carbide, or metal silicon carbonitride diffusion barrier layer.

A tantalum nitride barrier layer can be deposited by a PVD (orsputtering) process, such as that described in International patentApplication WO 99/53114 and by Mehrotra in a paper “Properties of DirectCurrent Magnetron Reactively Sputtered TaN” published in J. Vac. Sci.Technology, 1987. If the PVD (or sputtered) TaN does not contain TaNwith a substantially (111) preferred orientation, the film may beexposed to an adhesion promoting agent such as nitrogen or plasmaactivated nitrogen, or any of the other adhesion promoting agentsdisclosed herein, prior to forming the metal layer.

A tungsten nitride barrier layer can be deposited by a CVD process, suchas that described in International patent Application WO 99/00830. Ifthe CVD deposited WN barrier layer does not contain WN with asubstantially (111) preferred orientation, the film may be exposed to anadhesion promoting agent such as nitrogen or plasma activated nitrogen,or any of the other adhesion promoting agents disclosed herein, prior toforming the metal layer.

A titanium nitride barrier layer can be deposited by a PVD (orsputtering) process, such as that described, for example, in JapanesePatent Application 96127870 and U.S. Pat. Nos. 5,521,120; 5,242,860; and5,434,044. The titanium nitride barrier layer may also be deposited by asputtering process such as that described by Chen et al. in a paper“Evaluation of Radio-Frequency Sputtered-Deposited Textured TiN ThinFilms as diffusion Barriers between Copper and Silicon” published in J.Vac. Sci. Technology, 2002 and by Li in a paper “Initial Growth andTexture Formation During Reactive Magnetron Sputtering of TiN onSi(111)” published in J. Vac. Sci. Technology, 2002. If the PVD (orsputtered) TiN does not contain TiN with a substantially (111) preferredorientation, the film may be exposed to an adhesion promoting agent suchas nitrogen or plasma activated nitrogen, or any of the other adhesionpromoting agents disclosed herein, prior to forming the metal layer.

A titanium nitride barrier layer can be deposited by a CVD process suchas that described, for example, by Weiller in a paper “CVD of TitaniumNitride for Electronic Applications: Gas Phase Chemical Kinetics forFundamental Principles and Modeling” published in ElectrochemicalSociety Proceedings, 1996, by Buiting et al. in a paper “KineticalAspects of the LPCVD of Titanium Nitride from Titanium Tetrachloride andAmmonia” published in J. Electrochem. Society, 1991, and by Boutevillein a paper “Low Temperature Rapid Thermal Low Pressure Chemical VaporDeposition of (111) Oriented TiN Layers from the TiCl₄—NH₃—H₂ GaseousPhase” published in Microelectronic Engineering, 1997. If the CVDdeposited TiN does not grow with a substantially (111) preferredorientation, the film may be exposed to an adhesion promoting agent suchas nitrogen or plasma activated nitrogen, or any of the other adhesionpromoting agents disclosed herein, prior to forming the metal layer.

In embodiments wherein the barrier layer is exposed to an adhesionpromoting agent, the exposure may occur prior to or during at least aportion (preferably the initial portion) of the formation of the metalfilm. The temperature of the exposure step is preferably about 40 toabout 400° C., more preferably 100 to 400° C. The duration of theexposure step is preferably about 0.1 to about 10 minutes, morepreferably 0.1 to 2 minutes. The pressure during exposure is preferablyabout 10⁻⁹ torr to 400 torr, more preferably 1 millitorr to 100 torr.

As mentioned previously, at least one organometallic precursor is usedto form the metal or copper film using a CVD or an ALD process. Theorganometallic precursor may be used by itself or in a mixture withother organometallic compounds depending upon the composition of themetal film to be deposited. Exemplary organometallic precursor compoundsinclude organometallic copper precursors, organometallic platinumprecursors, organometallic nickel precursors, organometallic cobaltprecursors, organometallic palladium precursors, etc.

In certain embodiments of the present invention, the organometallicprecursor may be a non-fluorinated organometallic compound such as thecompound represented by the structure (I):

In structure (I), M and M′ are each a metal such as Cu, Ag, Au, and Ir;X and X′ can be N or O; Y and Y′ can be Si, C; Sn, Ge, B or Al; and Zand Z′ can be C, N, or O. Substituents represented by R1, R2, R3, R4,R5, R6, R1′, R2′, R3′, R4′, R5′, and R6′ will vary depending on the ringatom to which they are attached. In one embodiment of the presentinvention wherein a copper film is formed M and M′ are each Cu; X and X′are each N; Y and Y′ are each Si; Z and Z′ are each C; R1, R2, R1′, andR2′ are each independently an alkyl, an alkenyl, an alkynyl, a partiallyfluorinated alkyl, an aryl, an alkyl-substituted aryl, a partiallyfluorinated aryl, a fluoroalkyl-substituted aryl, a trialkylsilyl, or atriarylsilyl; R3, R4, R3′, and R4′ are each independently an alkyl, apartially fluorinated alkyl, a trialkylsilyl, a triarylsilyl, atrialkylsiloxy, a triarylsiloxy, an aryl, an alkyl-substituted aryl, apartially fluorinated aryl, a fluoroalkyl-substituted aryl, or analkoxy; and R5, R6, R5′, and R6′ are each independently a hydrogen, analkyl, an alkenyl, an alkynl, a partially fluorinated alkyl, an aryl, analkyl-substituted aryl, a partially fluorinated aryl, afluoralkyl-substituted aryl, a trialkylsilyl, a triarylsilyl, atrialkylsiloxy, triarylsiloxy, an alkoxy, a SiR7R8N(R9R10) group, or aSiR7R8OR11 group wherein R7, R8, R9, R10, and R11 can be an alkyl; andthe alkyl and alkoxide groups have from 1 to 8 carbons, the alkenyl andthe alkynyl groups have from 2 to 8 carbons; and the aryl group has 6carbons. Additional examples of non-fluorinated organometallicprecursors suitable for use with the present invention are provided inpending U.S. patent application Ser. No. 10/323,480 and U.S. Pat.Application, Atty. Docket No. 06414USA filed Apr. 22, 2003, which arepresently assigned to the assignee of the present invention.

In certain preferred embodiments of the present invention, at least oneorganometallic copper precursor is used to form a copper film. Theorganometallic copper precursor may be fluorinated or non-fluorinated.Examples of fluorinated compounds include, but are not limited to,compounds comprising hexafluoroacetylacetonate, most preferablyCu(I)(hfac)(tmvs). Examples of non-fluorinated organometallic copperprecursors include, but are not limited to, copper bis(acetylacetanoate), copper bis(2-dimethylaminoethoxide), andtetra(copper tert-butoxide).

The organometallic precursor may be added to the deposition chamber as amixture with other materials. Such materials include carrier gases whichmay be employed in transporting the gaseous phase precursors to thereaction chamber for lesser volatile precursors and enhance or otherwisecontrol the deposition rate. Examples of other compounds that can beadded to the deposition chamber include, but are not limited to, H₂O,tmvs, H₂, Ar, He, Kr, or Xe. The metal film of the present invention maybe deposited using any of the ALD or CVD processes disclosed herein.Processes of the invention are preferably conducted at ambient pressureor less, more preferably at a pressure of about 10⁻⁹ torr to 400 torr.Processes of the invention can be conducted at temperatures below roomtemperature and at temperatures typically achieved during deposition ofbarrier layers. Preferably, the processes are conducted at temperaturesranging from 50 to 400° C.

In one embodiment of the present invention, the metal film is formed byan ALD process. An example of an ALD process suitable for use with thepresent invention is provided in pending U.S. patent application Ser.No. 10/324,781. A metal film is deposited upon a substrate surface withthe desired diffusion barrier layer from at least two precursors: ahalogen-containing precursor and a metal-containing precursor. Examplesof suitable halogen-containing precursors include, but are not limitedto, halogen-containing silanes; alkylchlorosilanes, alkylbromosilanes,or alkyliodosilanes; silicon halide compounds such as silicontetrachloride, silicon tetrabromide, or silicon tetraiodide; halogenatedtin compounds such as alkylchlorostannanes, alkylbromostannanes, oralkyliodostannanes; germane compounds such as alkylchlorogermanes,alkylbromogermanes, or alkyliodiogermanes; boron trihalide compoundssuch as borontrichloride, boron tribromide, or boron triodide; aluminumhalide compounds such as aluminum chloride, aluminum bromide, oraluminum iodide; alkylaluminum halides; gallium halide compounds such asgallium trichloride, gallium tribromide, or gallium triodide; orcombinations thereof. Examples of suitable metal-containing precursorsinclude any of the organometallic precursors disclosed herein. A metalhalide layer is grown by sequentially introducing the halogen-containingprecursor and a metal-containing precursor into the process chamber. Themetal halide layer is then exposed to a reducing agent such as, but notlimited to, hydrogen gas, remote hydrogen plasma, silanes, boranes,alanes, germanes, hydrazines, or mixtures thereof.

Thin films may exhibit a range of atomic order from amorphous to highlycrystalline. A crystalline thin film may form as one single crystal witha specific crystallographic orientation relative to the substrate, or asan aggregate of crystals, with random or non-random orientations. XRD iscapable of distinguishing highly oriented single crystals orpolycrystalline films from polycrystalline films with randomorientation. It has been shown that a metal film such as a copper filmhaving (111) as the dominant texture or orientation is preferablebecause of its resistance to electromigration. Furthermore, it is widelyaccepted that a copper film deposited via a CVD process tends to formwith a preference for a (200) orientation on the most commonly utilizedbarrier layers, such as tantalum, while copper deposited via asputtering process on the same barrier layer tends to orient with apreference for a (111) texture which helps to enhance the electricalproperties of the copper. The invention described herein not onlyimproves the adhesion of copper but also promotes the growth of copperas well as other metal films with a preference for a (111) orientationif deposited onto a (111) oriented barrier layer.

The metal film of the present invention may be a substantiallycontinuous film, preferably having a thickness of at least 5 angstroms,more preferably from 5 to 6000 angstroms. In certain embodiments of thepresent invention, the metal or copper film may be used as aninterfacial layer and/or a seed layer at the top of the barrier layer.

The invention will be illustrated in more detail with reference to thefollowing Examples, but it should be understood that the presentinvention is not deemed to be limited thereto. In this connection, whilethe examples simulate the CVD deposition of a copper film using, it isunderstood that the present invention is suitable for deposition ofother metal films using organometallic precursors besides organometalliccopper precursors by CVD or ALD processes.

EXAMPLES

For the following examples, a number of theoretical calculations wereperformed based on periodic quantum mechanical density function theoryunder the generalized gradient approximation to study reactivity of aCUPRASELECT™ organometallic copper precursor with a variety of differentdiffusion barrier layers such as tantalum, tantalum nitride with (100)preferred orientation, tantalum nitride with a substantially (111)preferred orientation, tungsten, and tungsten nitride with asubstantially (111) preferred orientation. A series of ab initiomolecular dynamic simulations using different barrier layers wasperforming using the computer software program entitled “Siesta”developed by Sanchez-Portal, Ordejon, et al. (Refs. D. Sanchez-Protal,P. Ordejon, E. Artacho, and J. M. Soler, Int. J. Quantum Chem. 65, 453(1997); J. M. Soler, E. Artacho, J. D. Gale, A. Garcia, J. Junquera, P.Ordejon, and D. Sanchez-Portal, J. Phys. Condens. Matter 14, 2745(2002). Surface reactions including copper deposition were directlysimulated. The simulation methods were entirely base on physical firstprinciples without using empirical or experimental parameters and havebeen widely shown to be capable of providing accurate thermodynamic andkinetic data for a wide range of materials.

For the following examples, the structure of the Cu(I)(hfac)(tmvs) orCUPRASELECT™ molecule used was as follows:

The tantalum or tungsten barrier layer was simulated by using 3 atomiclayers of tantalum; whereas, the tantalum or tungsten nitride layer wassimulated by using 3 atomic layers of tantalum and 3 atomic layers ofnitrogen.

Example 1 Copper Deposited by CUPRASELECT™ Upon Tantalum Metal BarrierLayer Having (100) Preferred Orientation

An ab initio molecular dynamic computer simulation, based on periodicdensity function theory, was used to study the interaction betweenCUPRASELECT™ and a tantalum metal surface with a (100) preferredorientation. The simulation was performed at room temperature (25° C.)and near the CVD copper deposition temperature of 200° C. Thetheoretical results predicted that the CUPRASELECT™ molecule decomposedspontaneously upon exposure to a tantalum metal layer and formedtantalum carbides, oxides, and fluorides. The results also predictedthat the C—CF₃ bond in the ‘hfac’ ligand was the weakest bond within themolecule and can be easily broken into CF₃ groups. The energy requiredto break the C—CF₃ bond is ˜39 kcal/mol, which was considerably lowerthan the exothermic energy (˜260 kcal/mol) involved in the chemisorptionof CF₃ on the tantalum metal surface. This highly exothermic energywould be responsible for the further decomposition of CF₃ intofragments. Rather than volatilizing and escaping the deposition chamber,the fragments react with the tantalum surface, thereby forming afluorine, carbon and oxygen containing amorphous layer on the barrierlayer. This amorphous layer may lower the adherence of a copper layerwhen deposited onto the tantalum metal barrier layer.

Due to the formation of the amorphous layer, the present exampleillustrates that it may be difficult, if not impossible, to depositcopper adherently on tantalum metal by conventional CVD or ALDprocesses. The example also illustrates that the exothermic energyinvolved in chemisorption of the CF₃ radical on a barrier layer could beused indirectly to evaluate the interaction between the CUPRASELECT™molecule and the barrier layer and the adhesion of copper on the barrierlayer in subsequent examples. A high exothermic chemisorption energyresulting in fragmentation of the CF₃ radical would indicate pooradhesion of the copper deposited by CUPRASELECT™ on a barrier layer.

Example 2 Copper Deposited by CUPRASELECT™ Upon Tantalum Nitride BarrierLayer Having (100) Orientation

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tantalum nitride surface with a (100) preferred orientationand fragments or dissociated species of the CUPRASELECT™ molecule andtantalum nitride surface. The tantalum nitride contained 50:50 tantalumand nitrogen atoms. The tantalum nitride surface with (100) orientation,according to quantum mechanical calculations, contains alternatingtantalum and nitrogen atoms on the surface. This indicates that theCUPRASELECT™ molecule will be exposed to a diffusion barrier surfacecontaining tantalum atoms. Like Example 1, the interaction between theCUPRASELECT™ molecule and the tantalum nitride surface with (100)preferred orientation was determined by the exothermic energy involvedin the chemisorption of the CF₃ radical on the tantalum nitride barrierlayer.

The theoretical results predicted exothermic chemisorption energyof >125 kcal/mol. This energy was noted to be more than sufficient todecompose the CUPRASELECT™ molecule on the tantalum nitride surface withthe (100) preferred orientation and cause reaction between the CF₃radical and the tantalum nitride barrier layer. This would result informing the fluorine, carbon and oxygen containing amorphous layer onthe barrier layer and poor adhesion of CVD or ALD deposited copper onthe barrier layer.

The theoretical results from the computer simulation indicated that theCF₃ radical was selectively adsorbing on the tantalum atoms, decomposinginto further fragments, and then reacting with the tantalum atoms.Interestingly, however, no adsorption of the CF₃ radical was observed onthe nitrogen atoms. These results indicated that exposure of tantalumatoms was responsible for the exothermic chemisorption and decompositionof the CF₃ radical on the tantalum nitride surface with (100) preferredorientation. This example revealed that it would not be technicallyfeasible to deposit copper adherently on tantalum nitride surface with(100) preferred orientation as long as tantalum atoms are exposed to theCUPRASELECT™ molecule and its fragments.

Example 3 Copper Deposited by CUPRASELECT™ Upon Tantalum Nitride BarrierLayer Having a Substantially (111) Preferred Orientation

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tantalum nitride surface with a substantially (111)preferred orientation and fragments or dissociated species of theCUPRASELECT™ molecule and tantalum nitride surface. The tantalum nitridecontained 50:50 tantalum and nitrogen atoms. The tantalum nitridesurface with a substantially (111) preferred orientation, according toquantum mechanical calculations, contains tantalum atoms that arelocated underneath the nitrogen atoms. This means that the CUPRASELECT™molecule will not be directly exposed to tantalum atoms. Like theprevious examples, the interaction between the CUPRASELECT™ molecule andthe tantalum nitride surface with (111) preferred orientation wasdetermined by the exothermic energy involved in adsorbing the CF₃radical on the tantalum nitride barrier layer.

The theoretical results predicted exothermic chemisorption energy of <55kcal/mol, insufficient to overcome both the activation energy and bondof the C—CF₃ bond in the CUPRASELECT™ molecule in addition to supplying˜39 kcal/mol bond energy required to decompose the CUPRASELECT™molecule.

A more careful look into the theoretical results indicated that the CF₃radicals were not adsorbed onto the tantalum nitride surface with asubstantially (111) preferred orientation. In fact, the computersimulation showed that the CF₃ radicals were repelled from the surface.This example revealed that it would be technically feasible to depositcopper adherently on tantalum nitride surface with a substantially (111)orientation. It also revealed that it would be technically feasible todeposit copper adherently on tantalum nitride surface as long astantalum atoms are not exposed to the CUPRASELECT™ molecule.

Example 4 Copper Deposited by CUPRASELECT™ Upon Tantalum Nitride BarrierLayer Having (100) Preferred Orientation After Exposure to Nitrogen Gas

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tantalum nitride surface with (100) preferred orientationafter exposure to nitrogen gas. The tantalum nitride contained 50:50tantalum and nitrogen atoms. The interaction between nitrogen gas andtantalum nitride surface with (100) preferred orientation was determinedby the exothermic energy involved in chemisorption of nitrogen on thetantalum nitride barrier layer.

The theoretical results predicted exothermic chemisorption energy of >97kcal/mol. This energy was more than sufficient to passivate the tantalumnitride surface with (100) preferred orientation with nitrogen as wellas burying tantalum atoms under the nitrogen atoms. This meant that atantalum nitride surface with (100) preferred orientation after exposureto an adhesion promoting agent such as nitrogen would not react with anydissociated CF₃ radicals. As a result, the formation of fluorine, carbonand oxygen-containing amorphous layer on the barrier layer would beavoided thereby providing good adhesion of CVD or ALD deposited copperon the barrier layer.

This example revealed that it would be technically feasible to depositcopper adherently on tantalum nitride surface with (100) preferredorientation provided that the tantalum nitride surface is pretreatedwith an adhesion promoting agent such as nitrogen prior to exposing itto the CUPRASELECT™ molecule and its fragments.

Example 5 Copper Deposited by CUPRASELECT™ Upon Tantalum Nitride BarrierLayer Having a Substantially (111) Preferred Orientation

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tantalum nitride surface with a substantially (111)preferred orientation. The simulation was performed at room temperature(25° C.) and near the CVD copper deposition temperature of 200° C. Thetheoretical results predicted that the CUPRASELECT™ molecule cleanlydeposited copper on the surface without decomposition of the ‘hfac’ligand and the protecting olefinic species. The results also revealedthat the remaining components of the CUPRASELECT™ molecule did notinteract with the surface and were readily removed from the surface inthe form of a gas.

This example confirmed the results described in Example 3. Furthermore,it confirmed that it would be technically feasible to deposit copperadherently on tantalum nitride surface with a substantially (111)preferred orientation.

Example 6 Copper Deposited by CUPRASELECT™ Upon Tungsten Barrier LayerHaving (100) Preferred Orientation

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tungsten surface with a (100) preferred orientation andfragments or dissociated species of the CUPRASELECT™ molecule andtungsten surface. The theoretical results predicted that CUPRASELECT™molecule decomposed spontaneously upon exposing to tungsten metal. Theenergy of 39 kcal/mol required to break the C—CF₃ bond within the ‘hfac’ligand was considerably lower than the exothermic energy (˜272.7kcal/mol) involved in the chemisorption of the CF₃ radical on thetungsten surface. This highly exothermic energy would be responsible forthe further decomposition of the CF₃ radical into fragments. Rather thanvolatilizing and escaping the deposition chamber, the fragments reactwith the tungsten surface, thereby forming a fluorine, carbon and oxygencontaining amorphous layer on the barrier layer. This amorphous layermay lower the adherence of a copper layer when deposited onto thetantalum barrier layer.

Due to the formation of the amorphous layer, the present exampleillustrates that it may be difficult, if not impossible, to depositcopper adherently on tungsten by conventional CVD or ALD processes.

Example 7 Copper Deposited by CUPRASELECT™ Upon Tungsten Nitride BarrierLayer Having a Substantially (111) Preferred Orientation

A computer simulation program applying the periodic density functiontheory was used to study the interaction between the CUPRASELECT™molecule and tungsten nitride surface with a substantially (111)preferred orientation and fragments or dissociated species of theCUPRASELECT™ molecule and tungsten nitride surface. The tungsten nitridecontained 50:50 tungsten and nitrogen atoms with the top layer tungstenatoms fully covered by a monolayer of nitrogen atoms. This means thatthe CUPRASELECT™ molecule will not be directly exposed to tungstenatoms. Like the previous examples, the interaction between theCUPRASELECT™ molecule and the tungsten nitride surface with asubstantially (111) preferred orientation was determined by theexothermic energy involved in adsorbing the CF₃ radical on the tungstennitride barrier layer.

The theoretical results predicted exothermic chemisorption energy of<57.4 kcal/mol. This energy was noted not to be sufficiently high toovercome both the activation barrier and the ˜39 kcal/mol required tobreak the C—CF₃ bond in the CUPRASELECT™ molecule This meant that thetungsten nitride surface with a substantially (111) preferredorientation would not facilitate reaction between the CF₃ radical andthe tungsten nitride barrier layer. This would result in avoiding theformation of fluorine, carbon and oxygen containing amorphous layer onthe barrier layer and providing good adhesion of CVD copper on thebarrier layer.

This example revealed that it would be technically feasible to depositcopper adherently on tungsten nitride surface with a substantially (111)preferred orientation. It also revealed that it would be technicallyfeasible to deposit copper adherently on tungsten nitride surface aslong as tungsten atoms are not exposed to the CUPRASELECT™ molecule.

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A process for forming a metal film on an at least one surface of adiffusion barrier layer, the process comprising: providing the at leastone surface of the diffusion barrier layer, wherein the diffusionbarrier layer comprises at least one material selected from the groupconsisting of a metal, a metal carbide, a metal nitride, a metalcarbonitride, a metal silicon carbide, a metal silicon nitride, a metalsilicon carbonitride, and mixtures thereof, wherein the diffusionbarrier layer is not substantially free of elemental metal becauseeither (i) the at least one material is the metal, (ii) the diffusionbarrier layer has an orientation other than a substantially (111)preferred orientation, or (iii) the diffusion barrier layer has lessthan 95% of a (111) preferred orientation; exposing the at least onesurface of the diffusion barrier layer to an at least one adhesionpromoting agent selected from the group consisting of a nitrogen, anitrogen-containing compound, a carbon-containing compound, a carbon andnitrogen containing compound, a silicon and carbon containing compound,a silicon, carbon, and nitrogen-containing compound or a mixturethereof, is conducted at a temperature of from 40° C. to 400° C. suchthat the at least one surface becomes substantially free of an elementalmetal; and forming the metal film on at least a portion of the surfacewith at least one organometallic precursor by either a chemical vapordeposition or an atomic layer deposition process, wherein theorganometallic precursor comprises a metal selected from the groupconsisting of copper, platinum, nickel, cobalt, palladium, ruthenium,rhodium, iridium, gold, silver, and mixtures thereof wherein theexposing step is conducted prior to the forming step.
 2. The process ofclaim 1 wherein the exposing step includes plasma activation.
 3. Theprocess of claim 1 wherein the chemical vapor deposition is at least oneprocess selected from the group consisting of thermal chemical vapordeposition, plasma enhanced chemical vapor deposition, remote plasmaenhanced chemical vapor deposition, plasma assisted chemical vapordeposition, cryogenic chemical vapor deposition, chemical assisted vapordeposition, hot-filament chemical vapor deposition, photo-initiatedchemical vapor deposition, or combinations thereof.
 4. The process ofclaim 1 wherein the diffusion barrier layer is a metal nitride selectedfrom the group consisting of chromium nitride, tantalum nitride,titanium nitride, tungsten nitride, molybdenum nitride, zirconiumnitride, vanadium nitride, and mixtures thereof.
 5. The process of claim4 wherein the metal nitride is selected from the group consisting oftantalum nitride, titanium nitride, and tungsten nitride.
 6. The processof claim 5 wherein the metal nitride is tantalum nitride.
 7. The processof claim 1 wherein said diffusion barrier layer is a metal carbideselected from the group consisting of chromium carbide, tantalumcarbide, titanium carbide, tungsten carbide, molybdenum carbide,zirconium carbide, vanadium carbide, and mixtures thereof.
 8. Theprocess of claim 1 wherein said diffusion barrier layer is a metalcarbonitride selected from the group consisting of chromiumcarbonitride, tantalum carbonitride, titanium carbonitride, tungstencarbonitride, molybdenum carbonitride, zirconium carbonitride, vanadiumcarbonitride, and mixtures thereof.
 9. The process of claim 1 whereinsaid diffusion barrier layer is a metal silicon nitride selected fromthe group consisting of tantalum silicon nitride, titanium siliconnitride, molybdenum silicon nitride, and mixtures thereof.
 10. Theprocess of claim 1 wherein said diffusion barrier layer is a metalsilicon carbide selected from the group consisting of tantalum siliconcarbide, titanium silicon carbide, and mixtures thereof.
 11. The processof claim 1 wherein said diffusion barrier layer is a metal siliconcarbonitride selected from the group consisting of silicon carbonitride,titanium silicon carbonitride, tantalum silicon carbonitride, andmixtures thereof.
 12. The process of claim 1 wherein said organometallicprecursor is non-fluorinated.
 13. The process of claim 1 wherein saidorganometallic precursor is fluorinated.
 14. The process of claim 13wherein said organometallic precursor compriseshexafluoroacetylacetonate.
 15. The process of claim 1 wherein saidorganometallic precursor comprises an organometallic copper precursor.16. The process of claim 15 wherein said organometallic copper precursoris 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato-copper (I)trimethylvinylsilane.
 17. The process of claim 1 wherein saidorganometallic precursor is a compound represented by the followingstructure (I):

wherein M and M′ are each Cu, Ag, Au, Ir, Ru, Rh, or Re; X and X′ areeach N or O; Y and Y′ are each Si, C, Sn, Ge, B, or Al; Z and Z′ areeach C, N, or O; R1, R2, R1′, and R2′ are each independently a hydrogen,an alkyl, an alkenyl, an alkynyl, a partially fluorinated alkyl, anaryl, an alkyl-substituted aryl, a partially fluorinated aryl, afluoralkyl-substituted aryl, a trialkylsilyl, or a triarylsilyl when Xand X′ are N; R1 and R1′ are each independently an alkyl, an alkenyl, analkynyl, a partially fluorinated alkyl, an aryl, an alkyl-substitutedaryl, a partially fluorinated aryl, a fluoralkyl-substituted aryl, atrialkylsilyl, or a triarylsilyl when X and X′ are O; R3, R4, R3′, andR4′ are each independently a hydrogen, an alkyl, a partially fluorinatedalkyl, a trialkylsilyl, a triarylsilyl, a trialkylsiloxy, atriarylsiloxy, an aryl, an alkyl-substituted aryl, a partiallyfluorinated aryl, a fluoroalkyl-substituted aryl, or an alkoxy; and R5,R6, R5′, and R6′ are each independently a hydrogen, an alkyl, analkenyl, an alkynyl, a partially fluorinated alkyl, an aryl, analkyl-substituted aryl, a partially fluorinated aryl, afluoralkyl-substituted aryl, a trialkylsiloxy, a triarylsiloxy, atrialkylsilyl, a triarylsilyl, or an alkoxy; provided that when X and X′are each 0, there is no substitution at R2 and R2′; further providedthat when Z and Z′ are each N, there is no substitution at R6 and R6′;further provided that when Z and Z′ are each 0, there is no substitutionat R5, R6, R5′, or R6′; said alkyl and alkoxide having 1 to 8 carbons;said alkenyl and alkynyl having 2 to 8 carbons; and said aryl having 6carbons.